Hydropower is a renewable resource that is derived from the force or energy of moving water. For centuries hydropower has been used to accomplish tasks such as milling, pumping, sawing timber, and manufacturing. More recently, hydropower's usefulness as a source for electric power generation has been more fully exploited and today comprises a significant portion of the world's electricity needs.
Hydroelectric power generation has been accomplished through the use of gravitational force of falling water. Hydroelectric power has been used worldwide to generate huge amounts of electricity from water stored behind massive dams. However, the efficacy of large hydroelectric power projects has been called into question because of the human, economic and environmental impacts of dam construction and maintenance.
Hydroelectric projects can be disruptive to the natural topography of the installation area, the surrounding aquatic ecosystems both upstream and downstream of the plant site, and to human habitation. These disruptions include inconsistent or nonexistent sediment suspension that damages river beds and banks, physical damage to fish and wildlife habitat, especially spawning and hatching grounds, and changes in water temperature that affect wildlife and fauna. Another deleterious effect of hydroelectric power stations is that they typically require reservoir creation, which submerges habitable land. Relocation during reservoir creation is not only necessary for wildlife, but also for humans living within planned reservoir boundaries. Man-made reservoirs of hydroelectric power plants in certain regions may also produce substantial amounts of methane and carbon dioxide because of decaying plant material resulting from the underwater anaerobic environment. Lastly, the possibility of a dam failure, either through construction flaws or via assault during wartime, sabotage, and/or terrorism, while remote, are a constant threat to humans, wildlife, and fauna alike.
Harnessing a waterway's kinetic energy to avoid the problems of large hydroelectric plants has been challenging. Placing hydroelectric turbines in a waterway will not result in significant power creation because the turbines are generally designed for directed flows and high head conditions, e.g., a dam or waterfall. Given some apparent similarities between the flow of wind and the flow of water, many others have tried to use modified wind turbine designs, e.g., waterproof, different blade designs, etc., to capture waterway energy. However, these implementations have failed to survive standard waterway conditions, suffering from sheared blades during standard river conditions and an inability to handle the torque produced by the flowing water. Obvious improvements like stronger materials for turbine blades have not proved sufficient to allow for sustainable operation.